If we regress the final margin on the “honesty gap” — the difference in the number of voters who think each candidate is honest and trustworthy — we come up with a nearly linear relationship. That is, this question is a pretty reasonable predictor of the final margin.

In this case, I have it predicting a 12-point win for Clinton in South Dakota and a 10-point win for Obama in Montana. However, the South Dakota result is a bit unusual in that it’s the first state where substantial majorities think both candidates are honest and trustworthy. South Dakotans like both their Dems; if they wind up picking Clinton tonight, it should not really be read as some kind of indictment of Obama.

We can perform the same calculation on the “satisfied if ____ wins the nomination” question, which the exit polls have been tracking for a little longer: